Investigation the Southern Oscillation Index Effect on Dry/Wet Periods in North of Iran

ABSTRACT: Most of researchers in synoptic studies believe, there is a relationship between climatic and hydrological phenomena in different corners of the world with EL-Nino and southern oscillations index. therefore in this research, seven synoptic stations containing long-term data selected and analyzed the rainfall data in a regional study and investigated the correlation between Southern Oscillations index and incidence of dry/wet periods in north of Iran. The results in 95% level of significance showed that, there is a significant relation between mean annual rainfall in north of Iran and Southern Oscillation index. It should be considered that the correlation index between these two parameters was not equal in different spots and it decreased considerably from west to east. Mean while, there was a negative Pearson correlation between this index and monthly/annual rainfall in north of Iran which occurs with a few months delay. Whereas changes of Southern Oscillation index in summer and autumn, mainly showed more correlation with its influence on the rainfall in March and such changes, during the winter and spring was effecting on the rainfall in January until August in north of Iran.